/*-
 * Copyright 2003-2005 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions 
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
*/

#include "bsdiff.h"
#include "../shared.h"

static void split(off_t *I,off_t *V,off_t start,off_t len,off_t h)
{
	off_t i, j, k, x, tmp, jj, kk;

	if(len < 16) 
	{
		for(k=start; k<start+len; k+=j) 
		{
			j=1;
			x=V[I[k]+h];
			for(i=1; k+i<start+len; i++) 
			{
				if(V[I[k+i]+h] < x) 
				{
					x=V[I[k+i]+h];
					j=0;
				}
				if(V[I[k+i]+h] == x) 
				{
					tmp=I[k+j];
					I[k+j]=I[k+i];
					I[k+i]=tmp;
					j++;
				}
			}
			for(i=0; i<j; i++) 
				V[I[k+i]]=k+j-1;
			if(j == 1) 
				I[k]=-1;
		}
		return;
	}

	x=V[I[start+len/2]+h];
	jj=0;
	kk=0;
	for(i=start; i<start+len; i++) 
	{
		if(V[I[i]+h]<x) 
			jj++;
		if(V[I[i]+h]==x) 
			kk++;
	}
	jj+=start;
	kk+=jj;

	i=start;
	j=0;
	k=0;
	while(i < jj) 
	{
		if(V[I[i]+h] < x) 
		{
			i++;
		} 
		else if(V[I[i]+h] == x) 
		{
			tmp=I[i];
			I[i]=I[jj+j];
			I[jj+j]=tmp;

			j++;
		} 
		else 
		{
			tmp=I[i];
			I[i]=I[kk+k];
			I[kk+k]=tmp;

			k++;
		}
	}

	while(jj+j < kk) 
	{
		if(V[I[jj+j]+h] == x) 
			j++;
		else 
		{
			tmp=I[jj+j];I[jj+j]=I[kk+k];I[kk+k]=tmp;
			k++;
		}
	}

	if(jj > start) 
		split(I, V, start, jj-start, h);

	for(i=0; i<kk-jj; i++) 
		V[I[jj+i]] = kk-1;

	if(jj == kk-1) 
		I[jj] = -1;

	if(start+len > kk) 
		split(I, V, kk, start+len-kk, h);
}

static void qsufsort(off_t *I,off_t *V,u_char *old,off_t oldsize)
{
	off_t buckets[256];
	off_t i,h,len;

	for(i=0;i<256;i++) buckets[i] = 0;
	for(i=0;i<oldsize;i++) buckets[old[i]]++;
	for(i=1;i<256;i++) buckets[i]+=buckets[i-1];
	for(i=255;i>0;i--) buckets[i]=buckets[i-1];
	buckets[0] = 0;

	for(i=0;i<oldsize;i++) I[++buckets[old[i]]]=i;
	I[0] = oldsize;
	for(i=0;i<oldsize;i++) V[i]=buckets[old[i]];
	V[oldsize] = 0;
	for(i=1;i<256;i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;
	I[0] = -1;

	for(h=1;I[0]!=-(oldsize+1);h+=h) 
	{
		len=0;
		for(i=0;i<oldsize+1;) 
		{
			if(I[i]<0) 
			{
				len-=I[i];
				i-=I[i];
			} 
			else 
			{
				if(len) 
					I[i-len]=-len;
				
				len=V[I[i]]+1-i;
				split(I,V,i,len,h);
				i+=len;
				len=0;
			}
		}

		if(len) 
			I[i-len] = -len;
	}

	for(i=0; i<oldsize+1; i++) 
		I[V[i]]=i;
}

static off_t matchlen(u_char *old,off_t oldsize,u_char *new,off_t newsize)
{
	off_t i;

	for(i=0;(i<oldsize)&&(i<newsize);i++)
		if(old[i]!=new[i]) 
			break;

	return i;
}

static off_t search(off_t *I,u_char *old,off_t oldsize, u_char *new,off_t newsize,off_t st,off_t en,off_t *pos)
{
	off_t x, y;

	if(en-st < 2) 
	{
		x=matchlen(old+I[st],oldsize-I[st],new,newsize);
		y=matchlen(old+I[en],oldsize-I[en],new,newsize);

		if(x>y) 
		{
			*pos=I[st];
			return x;
		} 
		else 
		{
			*pos=I[en];
			return y;
		}
	}

	x=st+(en-st)/2;
	if(memcmp(old+I[x], new, (((oldsize-I[x])<(newsize)) ? (oldsize-I[x]) : (newsize))) < 0) 
		return search(I, old, oldsize, new, newsize,x, en, pos);
	else 
		return search(I, old, oldsize, new, newsize, st, x, pos);
}

static void offtout(off_t x,u_char *buf)
{
	off_t y;

	if(x<0) 
		y=-x; 
	else 
		y=x;

	buf[0]=y&0xff;y-=buf[0];
	y=y>>8;buf[1]=y&0xff;y-=buf[1];
	y=y>>8;buf[2]=y&0xff;y-=buf[2];
	y=y>>8;buf[3]=y&0xff;y-=buf[3];
	y=y>>8;buf[4]=y&0xff;y-=buf[4];
	y=y>>8;buf[5]=y&0xff;y-=buf[5];
	y=y>>8;buf[6]=y&0xff;y-=buf[6];
	y=y>>8;buf[7]=y&0xff;

	if(x < 0) 
		buf[7]|= 0x80;
}

int bsdiff(const char* error, const char* oldfile, const char* newfile, const char* patchfile, void* progressWorker, void(*callback)(off_t, off_t, void*)) 
{
	int fd;
	u_char *old,*new;
	off_t oldsize,newsize;
	off_t *I,*V;
	off_t scan,pos,len;
	off_t lastscan,lastpos,lastoffset;
	off_t oldscore,scsc;
	off_t s,Sf,lenf,Sb,lenb;
	off_t overlap,Ss,lens;
	off_t i;
	off_t dblen,eblen;
	u_char *db,*eb;
	u_char buf[24];
	t_header header;
	FILE * pf;
	BZFILE * pfbz2;
	int bz2err;

	/* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
		that we never try to malloc(0) and get a NULL pointer */
	if(((fd=open(oldfile,OPEN_FLAGS,0)) < 0) ||
		((oldsize=lseek(fd,0,SEEK_END))==-1) ||
		((old=malloc(oldsize+1))==NULL) ||
		(lseek(fd,0,SEEK_SET)!=0) ||
		(read(fd,old,oldsize)!=oldsize) ||
		(close(fd)==-1)) 
	{
			sprintf((char*)error, "\"%s\" %s", oldfile, strerror(errno));
			return -1;
	}

	if(((I=malloc((oldsize+1)*sizeof(off_t)))==NULL) ||
		((V=malloc((oldsize+1)*sizeof(off_t)))==NULL)) 
	{
		sprintf((char*)error, "%s", strerror(errno));
		return -1;
	}
	
	qsufsort(I,V,old,oldsize);

	free(V);
	
	/* Allocate newsize+1 bytes instead of newsize bytes to ensure
		that we never try to malloc(0) and get a NULL pointer */
	if(((fd=open(newfile,OPEN_FLAGS,0))<0) ||
		((newsize=lseek(fd,0,SEEK_END))==-1) ||
		((new=malloc(newsize+1))==NULL) ||
		(lseek(fd,0,SEEK_SET)!=0) ||
		(read(fd,new,newsize)!=newsize) ||
		(close(fd)==-1)) 
	{
			sprintf((char*)error, "\"%s\" %s", newfile, strerror(errno));
			return -1;
	}
	
	if(((db=malloc(newsize+1))==NULL) || ((eb=malloc(newsize+1))==NULL)) 
		err(1,NULL);
	
	dblen=0;
	eblen=0;
		
	/* Create the patch file */
	if((pf = fopen(patchfile, FOPEN_WRITE_FLAGS)) == NULL) 
	{
		sprintf((char*)error, "\"%s\" %s", patchfile, strerror(errno));
		return -1;
	}	
	
	/* Header is
		0	8	 "BSDIFF40"
		8	8	length of bzip2ed ctrl block
		16	8	length of bzip2ed diff block
		24	8	length of new file */
	/* File is
		0	32	Header
		32	??	Bzip2ed ctrl block
		??	??	Bzip2ed diff block
		??	??	Bzip2ed extra block */
	memcpy(header.magic,"BSDIFF40",8);
	offtout(0, (u_char*)&header.bzctrllen);
	offtout(0, (u_char*)&header.bzdatalen);
	offtout(newsize, (u_char*)&header.newsize);
	if(fwrite(&header, 32, 1, pf) != 1) 
	{
		sprintf((char*)error, "\"%s\" %s", patchfile, strerror(errno));
		return -1;
	}		

	/* Compute the differences, writing ctrl as we go */
	if((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL) 
	{
		sprintf((char*)error, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
		return -1;
	}	
	
	scan=0;
	len=0;
	lastscan=0;
	lastpos=0;
	lastoffset=0;

	while(scan<newsize) 
	{
		if(callback)
			callback(scan, newsize, progressWorker);
		oldscore=0;

		for(scsc=scan+=len;scan<newsize;scan++) 
		{
			len=search(I,old,oldsize,new+scan,newsize-scan,
					0,oldsize,&pos);

			for(;scsc<scan+len;scsc++)
			if((scsc+lastoffset<oldsize) && (old[scsc+lastoffset] == new[scsc]))
				oldscore++;

			if(((len==oldscore) && (len!=0)) || (len>oldscore+8)) 
				break;

			if((scan+lastoffset<oldsize) && (old[scan+lastoffset] == new[scan]))
				oldscore--;
		}

		if((len!=oldscore) || (scan==newsize)) 
		{
			s=0;
			Sf=0;
			lenf=0;

			for(i=0;(lastscan+i<scan)&&(lastpos+i<oldsize);) 
			{
				if(old[lastpos+i]==new[lastscan+i]) s++;
				i++;
				if(s*2-i>Sf*2-lenf) { Sf=s; lenf=i; }
			}

			lenb=0;
			if(scan<newsize) 
			{
				s=0;Sb=0;
				for(i=1;(scan>=lastscan+i)&&(pos>=i);i++) 
				{
					if(old[pos-i]==new[scan-i]) 
						s++;
					if(s*2-i>Sb*2-lenb) 
					{ 
						Sb=s; 
						lenb=i; 
					}
				}
			}

			if(lastscan+lenf>scan-lenb) 
			{
				overlap=(lastscan+lenf)-(scan-lenb);
				s=0;
				Ss=0;
				lens=0;
				for(i=0;i<overlap;i++) 
				{
					if(new[lastscan+lenf-overlap+i] == old[lastpos+lenf-overlap+i]) 
					s++;

					if(new[scan-lenb+i] == old[pos-lenb+i]) 
						s--;

					if(s>Ss) 
					{ 
						Ss=s; 
						lens=i+1; 
					}
				}

				lenf+=lens-overlap;
				lenb-=lens;
			}

			for(i=0;i<lenf;i++)
				db[dblen+i]=new[lastscan+i]-old[lastpos+i];
			if ((scan-lenb)-(lastscan+lenf) > 0)
				memcpy(&eb[eblen], &new[lastscan+lenf], (scan-lenb)-(lastscan+lenf));

			dblen+=lenf;
			eblen+=(scan-lenb)-(lastscan+lenf);

			offtout(lenf,&buf[0]);
			offtout((scan-lenb)-(lastscan+lenf),&buf[8]);
			offtout((pos-lenb)-(lastpos+lenf),&buf[16]);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 24);
			if (bz2err != BZ_OK) 
			{
				sprintf((char*)error, "BZ2_bzWrite, bz2err = %d", bz2err);
				return -1;
			}

			lastscan=scan-lenb;
			lastpos=pos-lenb;
			lastoffset=pos-scan;
		}
	}
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
	if (bz2err != BZ_OK) 
	{
		sprintf((char*)error, "BZ2_bzWriteClose, bz2err = %d", bz2err);
		return -1;
	}	

	/* Compute size of compressed ctrl data */
	if ((len = ftell(pf)) == -1) 
	{
		sprintf((char*)error, "\"ftell\" %s", strerror(errno));
		return -1;
	}		
	offtout(len-32, (u_char*)&header.bzctrllen);

	/* Write compressed diff data */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL) 
	{
		sprintf((char*)error, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
		return -1;
	}
	
	BZ2_bzWrite(&bz2err, pfbz2, db, dblen);
	if (bz2err != BZ_OK) 
	{
		sprintf((char*)error, "BZ2_bzWrite, bz2err = %d", bz2err);
		return -1;
	}
	
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
	if (bz2err != BZ_OK) 
	{
		sprintf((char*)error, "BZ2_bzWriteClose, bz2err = %d", bz2err);
		return -1;
	}	

	/* Compute size of compressed diff data */
	if ((newsize = ftell(pf)) == -1) 
	{
		sprintf((char*)error, "\"ftell\" %s", strerror(errno));
		return -1;
	}	
	offtout(newsize - len, (u_char*)&header.bzdatalen);

	/* Write compressed extra data */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL) 
	{
		sprintf((char*)error, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
		return -1;
	}
	
	BZ2_bzWrite(&bz2err, pfbz2, eb, eblen);
	if (bz2err != BZ_OK) 
	{
		sprintf((char*)error, "BZ2_bzWrite, bz2err = %d", bz2err);
		return -1;
	}
	
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
	if (bz2err != BZ_OK) 
	{
		sprintf((char*)error, "BZ2_bzWriteClose, bz2err = %d", bz2err);
		return -1;
	}		

	/* Seek to the beginning, write the header, and close the file */
	if (fseek(pf, 0, SEEK_SET)) 
	{
		sprintf((char*)error, "\"fseek\" %s", strerror(errno));
		return -1;
	}	
	if (fwrite(&header, 32, 1, pf) != 1) 
	{
		sprintf((char*)error, "\"%s\" %s", patchfile, strerror(errno));
		return -1;
	}	
	if (fclose(pf)) 
	{
		sprintf((char*)error, "\"fclose\" %s", strerror(errno));
		return -1;
	}
	
	/* Free the memory we used */
	free(db);
	free(eb);
	free(I);
	free(old);
	free(new);

	return 0;
}